1. Field of the Invention
The present invention relates to vehicle brake test systems and, in particular, to vehicle brake test systems for automotive vehicles, such as trucks having primary and secondary air brake systems.
2. Discussion of Related Art
Large tractor-trailer type trucks have air actuated brakes that are divided into primary and secondary systems. A secondary brake system is typically provided for the directional steering axle wheels of the vehicle. A primary brake system is typically provided for braking the drive axle wheels of the vehicle.
When testing a vehicle with air actuated brakes having a primary and secondary system, it is typically required that the brakes be applied at a consistent set pressure for many successive brake applications or stops. The air brake system must typically be tested while functioning under a wide pressure supply range. The pressure supply range can easily vary between 5-120 psi.
It is also often desirable that the vehicle brake system be tested utilizing only the secondary brake system or the primary brake system. Often, the brake system of vehicles is tested in a real life environment on an outdoor test track. When the vehicle is tested at low air pressures, the vehicle""s deceleration is at a slower pace with expanded stopping distances. During a slow pace deceleration, unanticipated events may occur, which require immediate emergency override of the system, such as a deer or another test vehicle in the vicinity. If an unanticipated event does occur, it is desirable to allow the vehicle operator to immediately utilize the brakes at their maximum capacity.
To make manifest the above delineated and other desires, a revelation of the present invention is brought forth. In a preferred embodiment, the present invention provides a test system for a vehicle having primary and secondary air brakes.
A first valve is provided. The first valve has a first inlet coupled to a primary air supply and a second inlet coupled to a test air supply. An outlet of the first valve is coupled to the brakes of the primary brake system of the vehicle.
A second valve is provided. The second valve has a first inlet coupled to a secondary air supply. The second valve also has a second inlet coupled to the test air supply. The second valve has an outlet coupled to the brakes of the secondary brake system of the vehicle.
A system selector switch assembly is provided. The system selector switch assembly selectively provides current to one or both of the first and second valves responsive to an operator input wherein each of the first and second valves directs fluid flow from one of the first and second inlets to the outlet.
There is additionally provided an override switch which will cause the first and second valves to couple their first inlet with their outlet, regardless of a selected position of the selector switch assembly. The override switch will typically be actuated by the operator of the vehicle utilizing the brake pedal (commonly referred to as the treadle).
Advantages of the present invention will be further explained as the invention is revealed in the accompanying drawings and detailed description.